Installing Capacitor Kits
This is just a quick document that I've put together to share some tips on installing cap kits.
Contents |
Expectations
An important fact: If you have a device that is behaving badly, a cap kit is not guaranteed to fix the problem. The only thing a cap kit does is ensure that your capacitors are operating within spec.
Capacitors are a frequent scapegoat. For some devices, they deserve to be so (See: Category:Bad_Capacitors). For others, they may not be to blame. That determination should be made by following proper troubleshooting procedures.
Post-install Adjustments
For certain devices, installing the cap kit may only be the first step in the process. Devices such as monitors and CD drives may require electrical adjustments once the kit has been installed.
After recapping a monitor, at the very least you shoul make sure that B+ is within spec. Leave the monitor powered up for a minimum of 30-60 minutes post installation to make sure it functions properly when warm.
For CD players, test behavior both before & after cap installation. Make sure that CDs are recognized quickly, that skipping back & forth across tracks works quickly, that the player is reasonably immune to skipping when the surface that it's sitting on is tapped, and that there are no unusual noises during playback. You probably will not have to make adjustments due to the new capacitors, but the act of disassembling & reassembling the mechanism might affect physical tolerances within the unit. For example, the suspension may become bound up if the cables are not routed properly. If the device was previously adjusted to compensate for defective caps, you may have to readjust once the new parts are installed.
Again, CD player adjustment isn't normally a concern, just a possibility to be aware of.
Luckily, for most solid-state devices, you can simply install the new caps and be done with it!
Tools
Make sure that you have the proper tools and experience necessary. Some kits are easy to install, some require quite a bit of patience and organizational skills.
Replacement Parts
Be sure that you have the correct parts for the job. Smaller devices will probably require smaller parts. Switch-type power supplies require low ESR caps. Some devices use higher heat tolerance parts, some use lower. Bipolar electrolytic capacitors look just like normal electrolytic caps except they have no orientation - don't mix & match!
Organization
If you've bought a pre-made cap kit, chances are that the values in the kit won't exactly match the values in the original device. This may be so for a variety of reasons, like decreasing kit cost, improving long-term reliability, or simply because an exact match is unavailable. Many times there are price breaks available on higher-voltage rated parts simply because they are more commonly used. With capacitors, you can safely go up in voltage ratings.
What I like to do is take a divided hobby storage box, like the kind people use for beads, and turn it sideways so I'm looking at four columns of storage compartments.
I open the kit and organize the parts in the box. The first column is for capacitors starting with 1 (1uf, 10uf, etc.), the second column for 2 (.22uf, 220uf, etc.), and so on. I organize the rows by capacitance, and then voltage, and then size.
The result is that as old caps are removed from the device, I can easily locate the new replacement caps.
Things to Remember Before You Begin
Installing kits in monitors can be hazardous. Discharge CRTs and follow all safety precautions.
If you have a digital camera, you will not regret taking several reference photographs during the procedure. That way, if you have any doubt about what size screws go where, what order to reassemble, which cable plugs into what jack, capacitor orientation, anything of this nature, you'll have a time-saving record on hand.
Cap Replacement
One by one, I remove each old capacitor. Before removing, I note its polarity, and whether the PCB has a silkscreen marking the correct polarity. If the board is not properly screened, you may want to use a marker to make a - or + mark on the PCB to indicate polarity.
Is the old cap "axial" and the new cap "radial"? Converting from Axial to Radial Capacitors
Is the old cap surface mount and the new cap a traditional, aka "leaded" part? Converting from Surface to Leaded Capacitors
With old cap in hand, find the replacement part that is closest in voltage & size. Some kits may have the same value, say 10uF, but several different voltages, so don't just pick out the first one you find (this is where being organized helps).